The field of this invention is that of removing unwanted water from deepwater pipelines. In some cases methane and other desirable gases will be produced from subsea wells and brought to the surface for initial processing. A prime function of this pre-processing is to remove the water from the gas.
After processing, the gasses will be returned to and along a seafloor pipeline for delivery to a remote location, also at sea level. As the high volume of gasses are passed into the pipeline, some portion of liquids will also reach the pipeline. These liquids, primarily water, will accumulate in the lowest points of the pipelines.
There are pipelines which have each end above sea level, and go through seafloor valleys as deep at 11,000 ft. deep. If a small amount of water accumulates in the pipeline, flowing gasses will simply percolate thru the water. The gas will push the water down on the near side and up on the far side until gas reaches the lowest point. At this time gas passes under the lowest point inside the pipeline and percolates up the far side. If there is enough water in the pipeline to raise the elevation of the water on the downstream side up 100 feet, it will take about 46.5 p.s.i. in gas pressure to do this (salt water is about 0.465 p.s.i./ft.). If you have gas supply pressure of 2,000 p.s.i., it will lift the gas on the downstream side by 4301 feet. If the pipeline depth is greater than 4301 feet, the pipeline is effectively completely blocked. Accumulated salt water in the 11,000 foot deep pipeline would be able to block a pressure of 5,115 p.s.i. (0.465*11,000).